Portable power tools having various different means for conducting or charging a combustible fuel into a suitable combustion chamber are of course well-known. An example of such a portable power tool is disclosed within U.S. Pat. No. 4,905,634 which issued to Veldman on Mar. 6, 1990. In accordance with the particular structure comprising the portable power tool of Veldman, the portable power tool disclosed therein utilizes any one of various gaseous fuels, such as, for example, compressed natural gas, a liquid petroleum gas, butane, or the like, and in order to effectively predetermine the rate at which the gaseous fuel is supplied to the power tool combustion chamber, a manually controlled adjusting screw or metering valve is utilized for the fine adjustment of the incoming gas supply. In addition, the introduction of the incoming gaseous fuel, as determined by means of the aforenoted manually controlled adjusting screw or metering valve, is also utilized to effectively induce or entrain the flow of ambient air into the combustion chamber of the power tool either for scavenging purposes in connection with residual gases that will be present within the combustion chamber upon completion of a particular power tool firing cycle, or for charging purposes in connection with the initiation of a subsequent power tool firing cycle. While the portable power tools, as exemplified by means of the portable power tool disclosed within the Veldman patent, are generally satisfactory, it is noted that such portable power tools nevertheless do exhibit some operational drawbacks or limitations.
For example, as has been noted hereinbefore, such portable power tools are adapted for use in connection with gaseous fuels, not liquid fuels, however, it is often desirable to operate such portable power tools, or similar portable power tools, with liquid fuels. In addition, while the aforenoted manually controlled adjusting screw or metering valve can predetermine the rate at which the gaseous fuel is supplied to the power tool combustion chamber, it is important that a predetermined amount of the fuel be supplied into the power tool combustion chamber so as to achieve proper or more accurate stoichiometric air-fuel ratios. Still yet further, portable power tools such as those disclosed within Veldman are not concerned with multiple combustion chamber systems which are desired or required for achieving predetermined combustion and power output characteristics or parameters.
A need therefore exists in the art for a new and improved fuel supply and combustion chamber system for a portable power tool, such as, for example, a fastener-driving tool, wherein the fuel supply and combustion chamber system can utilize liquid fuels, wherein the fuel supply and combustion chamber system can comprise multiple combustion chamber systems for achieving predetermined combustion and power output characteristics or parameters, and wherein the fuel supply and combustion chamber system can utilize portioning valve structures for providing predetermined amounts of either a gaseous or liquid fuel into the portable power tool combustion chamber.